Trilinear concrete model - con_tl

This is a simplified uniaxial trilinear concrete model that assumes no resistance to tension and features a residual strength plateau.

Five model calibrating parameters must be defined in order to fully describe the mechanical characteristics of the material:

Compressive strength - fc1
This is the cylinder compressive stress capacity of the material. Its value typically varies from 15 MPa up to 45 MPa. The default value is 28 MPa.

Initial stiffness - E1
This is the initial elastic stiffness of the material. Its value usually oscillates between 15 and 30 GPa. The default value is 20 GPa.

Post-peak stiffness - E2
This is the post-peak stiffness of the material. Its value commonly ranges from -5 to -30 GPa, depending on confinement characteristics. The default value is -10 GPa.

Residual strength - fc2
This is the residual stress capacity of the material. Its value normally fluctuates between 5 and 15 MPa. The default value is 5 MPa.

Specific weight -
This is the specific weight of the material. The default value is 24 kN/m3.

Notes

1. Values of compressive strength capacity obtained through testing of concrete cubes are usually 25 to 10 percent higher than their cylinder counterparts, for cylinder concrete strengths of 15 to 50 MPa, respectively.
2. Some researchers [e.g. Scott et al., 1982] have suggested that the influence of the high strain rates expected under seismic loading (0.0167/sec) on the stress-strain behaviour of the core concrete can be accounted for by adjusting the results of tests conducted at usual strain rates (0.0000033/sec); the adjustment could consist simply of applying a multiplying factor of 1.25 to the peak stress, the strain at the peak stress, and the slope of the post-yield falling branch. Mander et al. [1989] also present methods by which strain rate effects can be incorporated into the model, although the basic formulae, implemented here, do not include the effect.